Beam dumps having tailored absorbing surfaces

ABSTRACT

Laser energy has a non-uniform energy distribution in its profile such that at least one first portion of the laser energy is more intense than at least one second portion of the laser energy. The laser energy is absorbed using a beam dump having an absorbing surface, which converts the laser energy into thermal energy. A shape of the absorbing surface is based on the profile. At least one first portion of the absorbing surface has one or more first angles of incidence with respect to the laser energy and receives the first portion(s) of the laser energy. At least one second portion of the absorbing surface has one or more second angles of incidence with respect to the laser energy and receives the second portion(s) of the laser energy. The one or more first angles of incidence are larger than the one or more second angles of incidence.

CROSS-REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM

This application claims priority under 35 U.S.C. § 120 as a continuationof U.S. patent application Ser. No. 15/953,199 filed on Apr. 13, 2018(now U.S. Pat. No. 10,473,828), which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

This disclosure is generally directed to laser systems. Morespecifically, this disclosure is directed to beam dumps having tailoredabsorbing surfaces.

BACKGROUND

Conventional laser systems often include beam dumps, which are devicesconfigured to receive laser energy and to convert the laser energy intothermal energy. The thermal energy can then be removed from the beamdumps, such as by using cooling fluid (liquid or air) flowing throughthe beam dumps. The beam dumps therefore help to capture and removelaser energy from the laser systems. Beam dumps may be useful in varioussituations, such as when a residual laser beam is diverted to a beamdump during system shutdown or when laser energy needs to be captured sothat it does not damage sensitive components of a laser system.

SUMMARY

This disclosure provides beam dumps having tailored absorbing surfaces.

In a first embodiment, a system includes a laser configured to generatelaser energy having a profile. The laser energy has a non-uniform energydistribution in the profile such that at least one first portion of thelaser energy is more intense than at least one second portion of thelaser energy. The system also includes a beam dump having an absorbingsurface, where the absorbing surface is configured to absorb the laserenergy and convert the laser energy into thermal energy. A shape of theabsorbing surface is based on the profile of the laser energy such that(i) at least one first portion of the absorbing surface has one or morefirst angles of incidence with respect to the laser energy and isconfigured to receive the at least one first portion of the laser energyand (ii) at least one second portion of the absorbing surface has one ormore second angles of incidence with respect to the laser energy and isconfigured to receive the at least one second portion of the laserenergy. The one or more first angles of incidence are larger than theone or more second angles of incidence.

In a second embodiment, a method includes receiving laser energy havinga profile. The laser energy has a non-uniform energy distribution in theprofile such that at least one first portion of the laser energy is moreintense than at least one second portion of the laser energy. The methodalso includes absorbing the laser energy using a beam dump having anabsorbing surface, where the absorbing surface converts the laser energyinto thermal energy. A shape of the absorbing surface is based on theprofile of the laser energy such that (i) at least one first portion ofthe absorbing surface has one or more first angles of incidence withrespect to the laser energy and receives the at least one first portionof the laser energy and (ii) at least one second portion of theabsorbing surface has one or more second angles of incidence withrespect to the laser energy and receives the at least one second portionof the laser energy. The one or more first angles of incidence arelarger than the one or more second angles of incidence.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is madeto the following description, taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1A through 1D illustrate an example beam dump having an absorbingsurface tailored to a beam profile in one dimension for a high-energylaser system or other system according to this disclosure;

FIGS. 2 through 5 illustrate other example absorbing surfaces tailoredto beam profiles in one or more dimensions for use in beam dumpsaccording to this disclosure;

FIGS. 6A through 6E illustrate example beam profiles based on whichabsorbing surfaces of beam dumps could be tailored according to thisdisclosure;

FIGS. 7A and 7B illustrate example results that could be obtained usinga beam dump having an absorbing surface tailored to a beam profile for ahigh-energy laser system or other system according to this disclosure;

FIG. 8 illustrates an example high-energy laser system according to thisdisclosure; and

FIG. 9 illustrates an example method for fabricating and using a beamdump having an absorbing surface tailored to a beam profile in one ormore dimensions for a high-energy laser system or other system accordingto this disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 9, described below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the invention. Those skilled in the art willunderstand that the principles of the present invention may beimplemented in any type of suitably arranged device or system.

As noted above, a conventional laser system often includes a beam dump,which is used to convert laser energy into thermal energy in order toremove the laser energy from the laser system. Conventional beam dumpsoften include absorbing coatings and materials on the surfaces of thebeam dumps. These absorbing coatings and materials help to absorb laserenergy and convert the laser energy into thermal energy. Conventionalbeam dumps are often simply designed to absorb a certain amount of totallaser energy.

Unfortunately, in high-energy laser systems and other systems, laserbeams often do not have a uniform cross-sectional beam profile, whichmeans the beams have a non-uniform energy distribution across their beamprofiles. As a result, some areas of the beams are more intense and havelarger amounts of energy compared to other areas of the beams. When sucha beam strikes a conventional beam dump, certain portions of the beamdump can reach much higher temperatures than other portions of the beamdump.

Conventional beam dumps are not designed with the profiles of theincoming laser beams in mind. Rather, some conventional beam dumps aredesigned using coatings and materials (sometimes exotic) that canwithstand the maximum temperatures that are expected to be reached.Other conventional beam dumps are designed to include expensive orcomplex active cooling systems or larger surface areas, such as beamdumps that use inverted cones or specialty chambers in order to spreadlaser energy out over a larger area. While effective in some cases,these approaches still generally increase the cost or size of theconventional beam dumps and may experience operational issues inhigh-energy laser systems or other systems.

This disclosure provides various beam dumps having absorbing surfacesthat are tailored to the expected cross-sectional profiles of laserbeams to be received by the beam dumps. As described in more detailbelow, an absorbing surface of a beam dump includes a surface orcombination of surfaces (such as flat or curved surfaces) specificallyselected and constructed for a certain beam's cross-sectional profile.The surface or surfaces operate to spread out higher-intensity portionsof the beam to a greater extent using greater angles of incidence whileusing shallower angles of incidences for lower-intensity portions of thebeam. The spreading of the higher-intensity portions of the beam couldoccur in a single dimension or multiple dimensions of the beam profile,and the spreading reduces the maximum temperature experienced by thebeam dump.

By at least partially basing the shape of a beam dump's absorbingsurface on the expected profile of a beam, it is possible to optimizethe beam dump for a specific application. For example, the absorbingsurface can be designed to distribute more intense portions of aspecific profile beam over a larger portion of the absorbing surface,reducing the maximum temperature. It is also possible to optimize thebeam dump for use with specific absorbing coatings or materials. Amongother things, this may allow less complicated cooling systems to be usedin the beam dump or allow “weaker” materials that can withstand lowertemperatures to be used in the beam dump, which can reduce the cost ofthe beam dump. This may also allow for the beam dump's overall shape andsize to be tailored to any volume constraints associated with a specificapplication or use of the beam dump.

FIGS. 1A through 1D illustrate an example beam dump 100 having anabsorbing surface tailored to a beam profile in one dimension for ahigh-energy laser system or other system according to this disclosure.As shown in FIGS. 1A through 1C, the beam dump 100 includes a base 102and a housing 104. The base 102 generally represents a structure thatenables the beam dump 100 to be secured to other components of a lasersystem or other system. The base 102 could have any suitable form thatenables the beam dump 100 to be secured. In this example, the base 102includes multiple flanges 106 that project outward and include holes108. The holes 108 allow bolts or other connectors to pass through theflanges 106 and secure the base 102 (and therefore the beam dump 100) inplace. However, any other suitable mechanism could be used to secure thebeam dump 100.

The housing 104 generally represents a structure that receives laserenergy (here in the form of a laser beam 110) and converts the laserenergy into thermal energy. In this example, the housing 104 includes anabsorbing surface 112 a, which the beam 110 strikes. The absorbingsurface 112 a absorbs most or all of the energy in the beam 110, therebyterminating that laser energy and converting that laser energy intoheat. While a small portion of the laser energy in the beam 110 couldreflect from the absorbing surface 112 a, most or all of that reflectedlaser energy could be absorbed by other components of the housing 104.Ideally, the housing 104 terminates all of the laser energy contained inthe beam 110, although a very small amount of the laser energy containedin the beam 110 could escape the housing 104 without causing much if anydamage to a larger system.

The housing 104 also includes a cover 114 positioned above the absorbingsurface 112 a and a bottom 116 positioned below the absorbing surface112 a, as well as a side 118 extending between the cover 114 and thebottom 116. The absorbing surface 112 a, cover 114, bottom 116, and side118 generally form a cavity into which the beam 110 enters beforestriking the absorbing surface 112 a. Any laser energy that is notabsorbed by the absorbing surface 112 a and that reflects from theabsorbing surface 112 a could strike the cover 114, bottom 116, or side118 and be absorbed.

In this example, the side 118 includes one or more holes 120, which canbe used to allow bolts, screws, or other connectors to be used to securethe side 118 to the bottom 116 of the housing 104. Optionally, at leastone injection hole 122 a can be used to allow thermal paste to beinjected into any gap between the side 118 and the bottom 116, and atleast one witness hole 122 b can be provided to allow visual inspectionand confirmation that adequate thermal paste has been injected into thegap. Note, however, that the holes 122 a-122 b and the use of thermalpaste are optional. In this example, the housing 104 further includes aslot 124, which could be used to provide clearance for other componentsof a larger laser system. Note that the form of the slot 124 could varyas needed or desired, or the slot 124 could be omitted if not needed. Inthis example, the beam dump 100 is cooled passively, such as throughradiative or convective cooling. However, while not shown here, one ormore inlets and one or more outlets, as well as one or more internalpassageways, could be used to allow cooling fluid (such as liquid orair) to flow into and out of the beam dump 100 to provide activecooling. It should be noted that any other suitable passive or activecooling mechanisms could be used here.

The beam dump 100 could be formed from any suitable material(s) and inany suitable manner. For example, the base 102 and the housing 104 couldbe formed completely or primarily using aluminum, carbon, or steel,although more exotic materials could also be used. The absorbing surface112 a could be formed from the same material(s) as the housing 104, suchas when the absorbing surface 112 a includes surface features etchedinto or otherwise formed in or on the housing 104 to help absorb laserenergy. The absorbing surface 112 a could also be formed from differentmaterials than the housing 104, such as when the absorbing surface 112 arepresents oxidized or black anodized portions of the housing 104 or oneor more absorbing materials (like black chrome) deposited onto thehousing 104.

The specific material or materials used to form the base 102 and thehousing 104 can be based, at least in part, on the expected power of thebeam 110 and the expected volume of the cavity within the housing 104.As noted above, because the absorbing surface 112 a can be designedbased on the expected profile of the beam 110 in order to spread outmore intense portions of the beam 110, the base 102 and the housing 104could experience less localized heating from the beam 110. This allowsthe base 102 and the housing 104 to be formed using less expensivematerials, such as those having lower temperature damage thresholds.

The beam dump 100 could be formed as a single component or usingmultiple components that are coupled together in any suitable manner.For example, in some embodiments, the base 102 and the housing 104(minus the side 118) could be formed as a single integral structure, andthe side 118 could be formed separately and attached to the bottom 116of the housing 104. In other embodiments, the base 102 and the housing104 could be formed separately, and the housing 104 could be formedusing multiple pieces that are connected together. In still otherembodiments, the housing 104 could be formed as an integral structurethat is attached to the base 102, or the base 102 and the housing 104could be formed as a single integral structure. Also, each component ofthe beam dump 100 could be fabricated in any suitable manner, such ascasting, injection molding, additive or subtractive manufacturing, orother process.

FIG. 1A illustrates a perspective view of the beam 110 entering the beamdump 100 and striking the absorbing surface 112 a. FIG. 1B illustrates aside view of the beam 110 entering the beam dump 100 and striking theabsorbing surface 112 a. FIG. 1C illustrates a perspective view of thebeam 110 entering the beam dump 100 and striking the absorbing surface112 a, but the cover 114 and side 118 have been removed.

In the example shown in FIG. 1C, the absorbing surface 112 a is facetedwith three distinct flat faces 126 a-126 c. The faces 126 a and 126 cgenerally have a smaller angle of incidence with respect to the beam110, and the face 126 b generally has a larger angle of incidence withrespect to the beam 110. Each angle of incidence is defined as an anglebetween a line normal to a surface (any of the faces 126 a-126 c) and alongitudinal axis extending along the length of the beam 110.

Here, it is assumed that the beam profile of the beam 110 has a Gaussiandistribution, which means the intensity of the beam 110 is at a maximumat the center of the beam's cross-section and lessens moving outwardfrom the center. This type of distribution for the beam 110 isrepresented in FIG. 1D using different rings, where the different ringscorrespond to different intensities or intensity ranges within the beam110. The central area of the beam 110 is most intense, and each ringmoving outward from the center is generally less intense.

When a beam 110 such as this strikes the absorbing surface 112 a, acentral portion 128 of the beam 110 strikes the absorbing surface 112 aat a larger angle of incidence compared to outer portions 130 a-130 b ofthe beam 110. As a result, the central portion 128 of the beam 110expands over the absorbing surface 112 a to a larger extent than theouter portions 130 a-130 b of the beam 110. This is because the centralportion 128 strikes the face 126 b and the outer portions 130 a-130 bstrike the faces 126 a and 126 c, and the face 126 b has a larger angleof incidence than the faces 126 a and 126 c. Thus, while the face 126 bmay receive more energy from the beam 110, that energy is expanded overthe face 126 b more than the energy expands over the faces 126 a and 126c. The face 126 b therefore experiences less localized heating than itwould if it had a smaller angle of incidence with respect to the beam110. The faces 126 a and 126 c may receive less energy from the beam 110than the face 126 b, but that energy is expanded less (or not at all)compared to the face 126 b.

This approach therefore helps to distribute the energy from the beam 110more evenly across the absorbing surface 112 a. Ideally, the profile ofthe absorbing surface 112 a would match the beam profile of the beam 110such that the energy distribution would be completely uniform over theabsorbing surface 112 a. In reality, a non-uniform distribution of laserenergy over the absorbing surface 112 a (and therefore localized heatingof the absorbing surface 112 a) would typically occur, but it occurs toa much smaller extent compared to conventional beam dumps.

Note that in this particular example, the design of the absorbingsurface 112 a is only partially optimized, and the optimization occursin only one dimension. That is, the faces 126 a-126 c are arrangedlinearly, and the absorbing surface 112 a is designed to spread out theenergy in the beam 110 over a larger distance horizontally but notvertically in FIG. 1D. As a result, the energy from the beam 110 isdistributed onto an area of the absorbing surface 112 a that is largerhorizontally than the width of the beam 110 but that is substantiallythe same height as the beam 110. Here, the absorbing surface 112 aessentially spreads a circular beam 110 over an elliptical area of theabsorbing surface 112 a. Since the faces 126 a-126 c are generally flatin this example, the beam 110 is generally not widened vertically inFIG. 1D (although, as described below, other designs for the absorbingsurface could). The design is also said to be partially optimized heresince the beam 110 typically would not include only three clearlydistinct areas of different intensities. Even so, given this design forthe absorbing surface 112 a, the higher-intensity central portion 128 ofthe beam 110 expands more on the absorbing surface 112 a, reducing itsintensity of the face 126 b.

Because it is assumed here that the beam profile of the beam 110 has aGaussian distribution, the largest angle of incidence occurs in themiddle face 126 b of the absorbing surface 112 a. However, the beam 110could have another distribution of energy in its cross-section, in whichcase the numbers of faces and the angles of incidence of those facescould vary based on the different profile. For example, if the beam 110has a maximum intensity that is offset from its center, the face 126 bwould be moved to the appropriate offset location, while the sizes ofthe faces 126 a and 126 c would be adjusted accordingly. As anotherexample, if the beam 110 has a maximum intensity on one side and theintensity gradually decreases towards the other side, the face 126 acould have the largest angle of incidence, the face 126 b could have asmaller angle of incidence, and the face 126 c could have the smallestangle of incidence. Of course, other arrangements of the faces couldalso be used as needed based on the beam profile. In general, a widevariety of designs for the absorbing surface could be used, depending atleast in part on (i) the actual profile that the beam 110 is expected tohave, (ii) the number of dimensions to be optimized, and (iii) theamount of optimization to occur within the dimension(s).

FIGS. 2 through 5 illustrate other example absorbing surfaces tailoredto beam profiles in one or more dimensions for use in beam dumpsaccording to this disclosure. As shown in FIG. 2, an absorbing surface112 b is similar to the absorbing surface 112 a described above, but theabsorbing surface 112 b is more continuous and is not divided intodistinct flat faces. Instead, the absorbing surface 112 b transitionsfrom a first portion 226 a having smaller angles of incidence to asecond portion 226 b having larger angles of incidence and then to athird portion 226 c having smaller angles of incidence. Note that theabsorbing surface 112 b here is curved along most or all of its length,so each portion 226 a-226 c does not have a single angle of incidence aswith the absorbing surface 112 a. The portions 226 a-226 c areidentified here merely as a matter of convenience so that differentareas of the absorbing surface 112 b can be identified and discussed,without requiring each portion to have a single angle of incidence.

The different curvatures of the portions 226 a-226 c again can be basedat least partially on the expected profile of the beam 110. In thisexample, the beam 110 again is assumed to have a Gaussian profilesimilar to that shown in FIG. 1D. Because of this, the largest angles ofincidence occur in the middle of the absorbing surface 112 b, and theangles of incidence decrease non-linearly going towards the ends of theabsorbing surface 112 b. Of course, the largest angles of incidence inthe absorbing surface 112 b could be moved if the beam profile of thebeam 110 has a largest intensity elsewhere.

As with the absorbing surface 112 a, the absorbing surface 112 b here isdesigned to optimize the absorption of beam energy in a singledimension. This is because the portions 226 a-226 c are arrangedlinearly, and the beam 110 strikes the absorbing surface 112 b in anarea wider than the beam's width but about the same as the beam'sheight. However, the absorbing surface 112 b may be more fully optimizedthan the absorbing surface 112 a since the absorbing surface 112 b usescurved surfaces rather than flat faces. These curved surfaces may moreclosely follow the Gaussian distribution of laser energy in the beam110.

As shown in FIG. 3, an absorbing surface 112 c provides optimization inmultiple dimensions. Here, the absorbing surface 112 c generally takesthe form of an “exponential” cone, which describes a shape where theside of a cone is not a straight line rotated about an axis but ratheran exponential curve rotated about an axis. The absorbing surface 112 cgenerally transitions from a first portion 326 a having the largestangles of incidence (including a tip of the exponential cone) to asecond portion 326 b having smaller angles of incidence and then to athird portion 326 c having the smallest angles of incidence (including abase of the exponential cone). Again, the portions 326 a-326 c areidentified here merely as a matter of convenience so that differentareas of the absorbing surface 112 c can be identified and discussed,without requiring each portion to have a single angle of incidence.

The optimization of energy distribution onto the absorbing surface 112 coccurs in two dimensions here. This is because the absorbing surface 112c has different angles of incidence both horizontally and verticallyacross the absorbing surface 112 c (or in whatever other orthogonaldirections the dimensions are defined). The different curvatures of theportions 326 a-326 c again can be based at least partially on theexpected profile of the beam 110. In this example, the beam 110 againhas a Gaussian profile such as is shown in FIG. 1D. The largest anglesof incidence occur in the middle of the absorbing surface 112 c, and theangles of incidence decrease non-linearly going towards the outer edgeof the absorbing surface 112 c. Of course, the largest angles ofincidence in the absorbing surface 112 c could be moved if the beamprofile of the beam 110 has a largest intensity elsewhere. For instance,if the beam 110 is most intense in a non-central location, the peak ortip of the absorbing surface 112 c could be moved to and centered atthat location.

As shown in FIG. 4, an absorbing surface 112 d represents an invertedform of the absorbing surface 112 c. That is, rather than extendingupward towards the beam 110 as in the absorbing surface 112 c, theabsorbing surface 112 d extends downward and away from the beam 110.However, the absorbing surface 112 d still generally takes the form ofan exponential cone and transitions from a first portion 426 a havingthe largest angles of incidence (including a tip of the invertedexponential cone) to a second portion 426 b having smaller angles ofincidence and then to a third portion 426 c having the smallest anglesof incidence (including a base of the inverted exponential cone).

The optimization of energy distribution onto the absorbing surface 112 dagain occurs in two dimensions here since the absorbing surface 112 dhas different angles of incidence both horizontally and vertically (orin whatever other orthogonal directions the dimensions are defined).Also, the different curvatures of the portions 426 a-426 c again can bebased at least partially on the expected profile of the beam 110. Inthis example, the beam 110 has a Gaussian profile as in FIG. 1D, so thelargest angles of incidence occur in the middle of the absorbing surface112 d, and the angles of incidence decrease non-linearly going towardsthe outer edge of the absorbing surface 112 d. The largest angles ofincidence in the absorbing surface 112 d could be moved if the beamprofile of the beam 110 has a largest intensity elsewhere, such as whenthe deepest point of the absorbing surface 112 d is moved if the beam110 is most intense in a non-central location.

Note that while flat faces are not used in FIGS. 3 and 4, the sameapproach described with respect to the absorbing surface 112 a could beused with the absorbing surfaces 112 c and 112 d. In other words,sections of the absorbing surfaces 112 c and 112 d could be implementedusing flat surfaces instead of curved surfaces. This would still allowfor partial optimization of the beam energy distribution onto theabsorbing surfaces 112 c and 112 d, even if the distributions are notfully optimized.

As shown in FIG. 5, an absorbing surface 112 e represents a truncatedexponential cone, meaning the pointed tip of an exponential cone hasbeen removed. Here, the absorbing surface 112 e transitions from a firstportion 526 a (including a central portion of the truncated exponentialcone) to a second portion 526 b having the largest angles of incidenceand then to a third portion 526 c having smaller angles of incidence(including a base of the truncated exponential cone). In this example,the first portion 526 a is flat and perpendicular to the beam's axis.Although not shown here, an inverted form of the truncated exponentialcone could also be used as an absorbing surface.

The optimization of energy distribution onto the absorbing surface 112 eagain occurs in two dimensions here since the absorbing surface 112 ehas different angles of incidence both horizontally and vertically (orin whatever other orthogonal directions the dimensions are defined).Also, the different shapes of the portions 526 a-526 c can be based atleast partially on the expected profile of the beam 110. In thisexample, the beam 110 has an annular distribution of beam energy in itscross-section. The largest angles of incidence are in a ring around themiddle of the absorbing surface 112 e, and the angles of incidencedecrease non-linearly going towards the outer edge of the absorbingsurface 112 e. The central portion 526 a of the absorbing surface 112 eis flat since it may receive little or no beam energy, although thecentral portion 526 a of the absorbing surface 112 e could have otherforms if appropriate given the expected beam profile, such as a convexor concave shape (and possibly a very convex or concave shape).

Note that while a single flat face is used in FIG. 5, the same approachdescribed with respect to the absorbing surface 112 a could be used withthe absorbing surface 112 e. In other words, the portions 526 b-526 c ofthe absorbing surface 112 e could be implemented using flat surfacesinstead of curved surfaces. This would still allow for partialoptimization of the beam energy distribution onto the absorbing surface112 e, even if the distributions are not fully optimized.

Despite the different shapes of the absorbing surfaces 112 a-112 edescribed above, all of the absorbing surfaces 112 a-112 e operate usingthe same general principle. Each absorbing surface 112 a-112 e isdesigned as a single surface or a combination of surfaces (flat orcurved) based at least partially on the expected beam profile. At leastone surface or a portion thereof is designed and positioned to spreadout one or more higher-intensity portions of a beam 110. One or morelower-intensity portions of the beam 110 may or may not be spread outdepending on the absorbing surface. As a result of the spreading, laserenergy from the beam 110 is distributed more evenly (although notnecessarily uniformly) over the absorbing surface of the beam dump 100,and the maximum temperature experienced by the beam dump 100 decreases.

Although FIGS. 1A through 1D illustrate one example of a beam dump 100having an absorbing surface 112 a tailored to a beam profile in onedimension for a high-energy laser system or other system and FIGS. 2through 5 illustrate other examples of absorbing surfaces 112 b-112 etailored to beam profiles in one or more dimensions, various changes maybe made to FIGS. 1A through 5. For example, the base 102 and the housing104 could each have any other suitable size, shape, or dimensions. Also,any suitable active or passive cooling mechanism could be used to coolthe beam dump 100. In addition, the absorbing surfaces 112 a-112 e shownhere are examples only and are based on specific types of beam profilesthat may be encountered for the beam 110. However, other beam profilesare also possible, and the absorbing surfaces of the beam dump 100 couldbe modified in various ways to more closely match the energydistribution in a given beam 110.

FIGS. 6A through 6E illustrate example beam profiles based on whichabsorbing surfaces of beam dumps could be tailored according to thisdisclosure. In particular, FIGS. 6A through 6E plot beam intensitieswithin a cross-section of a beam 110 for different types of beamprofiles. Each of these beam profiles could represent the profile of thebeam 110 being used with the beam dump 100 described above. Note thatthis is not a complete illustration of all possible beam profiles and ismeant merely to illustrate examples of the types of beam profiles thatcould be used to tailor an absorbing surface of a beam dump.

In FIG. 6A, a beam profile 600 represents a Gaussian distribution ofenergy within a beam's cross-section. As described above, in a Gaussiandistribution, the intensity of the beam 110 is at a maximum at thecenter of the beam's cross-section and lessens moving outward from thebeam's center. The absorbing surfaces 112 a-112 b can be used with thisbeam profile 600 to optimize the distribution of energy onto the beamdump 100 in one dimension. Alternatively, the absorbing surfaces 112c-112 d can be used with this beam profile 600 to optimize thedistribution of energy onto the beam dump 100 in two dimensions, or theabsorbing surface 112 e could be modified so that the central portion526 a is convex or concave.

In FIG. 6B, a beam profile 620 represents a “mesa” or flat-topdistribution of energy within a beam's cross-section. Unlike theGaussian distribution in the beam profile 600 where only the very centerof the profile 600 reaches a maximum value, the beam profile 620indicates that a much larger area of the profile 620 reaches a maximumvalue. Also, the profile 620 ramps much more quickly from its outer edgeto the maximum value. A beam 110 having this type of profile 620 wouldnot have the large number of intensity rings as shown in FIG. 1D andwould instead have a more uniform energy distribution in a largerportion of the beam's cross-section. The same types of absorbingsurfaces 112 a-112 d could be used with the beam profile 620, but thecentral portions of the absorbing surfaces 112 a-112 d would be enlargedand the outer portions of the absorbing surfaces 112 a-112 d would benarrowed to accommodate the larger high-intensity area of the beamprofile 620. The absorbing surface 112 e could also be modified so thatthe central portion 526 a is larger and either convex or concave.

In FIG. 6C, a beam profile 640 represents an annular distribution ofenergy within a beam's cross-section and could represent the annularbeam 110 shown in FIG. 5. In this type of beam profile 640, beam energyis concentrated within a single ring around a center of the profile 640,and much less energy is contained outside the ring and inside the ring.The absorbing surfaces 112 a-112 b could be used with this type of beamprofile 640 to optimize the distribution of energy onto the beam dump100 in one dimension, or the absorbing surface 112 e could be used withthis beam profile 640 to optimize the distribution of energy onto thebeam dump 100 in two dimensions. Alternatively, one instance of theabsorbing surface 112 c or 112 d could be designed, positioned at adistance from a vertical axis, and rotated around the vertical axis toform a circular ridge or valley that follows the same pattern as theprofile 640. This would allow the highest or lowest points of theabsorbing surface 112 c or 112 d to follow the ring of the beam profile640.

In FIG. 6D, a beam profile 660 represents a Laguerre-Gaussiandistribution of energy within a beam's cross-section. Here, theLaguerre-Gaussian distribution includes an outer ring of higherintensity and an inner ring of higher intensity. Note that the relativeheights of the two rings could vary, and the outer ring may or may notbe higher in intensity than the inner ring. The absorbing surfaces 112a-112 b could be used with this type of beam profile 660 by increasingthe number of areas with larger angles of incidence and by increasingthe number of areas with smaller angles of incidence. Along onedimension, the areas with larger angles of incidence would be positionedto receive laser energy contained in the inner and outer rings of thebeam 110, and the areas with smaller angles of incidence would bepositioned to receive laser energy in other portions of the beam 110.For two-dimensional optimization, two instances of the absorbing surface112 c or 112 d could be designed, positioned at different distances froma vertical axis, and rotated around the vertical axis to form multiplecircular ridges or valleys that follow the same pattern as the profile660. This would allow the highest or lowest points of the two absorbingsurfaces 112 c or 112 d to follow the inner and outer rings of the beamprofile 660. Alternatively, the absorbing surface 112 e could be usedwith the inner ring of higher intensity in the beam profile 660, and araised ring (or one instance of the absorbing surface 112 c or 112 drotated around a vertical axis) could be used with the outer ring ofhigher intensity in the beam profile 660.

In FIG. 6E, various beam profiles 680 represent different exampleHermite-Gaussian distributions of energy within a beam's cross-section.Here, the Hermite-Gaussian distributions include different numbers ofsmaller peaks of higher intensity, and the number of peaks and thearrangement of those peaks vary in different Hermite-Gaussiandistributions. The absorbing surfaces 112 a-112 b could be used with anyof these beam profiles 680 by increasing the number of areas with largerangles of incidence and by increasing the number of areas with smallerangles of incidence. The areas with larger angles of incidence would bepositioned to receive laser energy in the peaks of the beam profiles680, and the areas with smaller angles of incidence would be positionedto receive laser energy in other portions of the beam profiles 680. Thesizes of the areas with larger angles of incidence can vary since thesizes of the peaks in the different beam profiles 680 can also vary. Fortwo-dimensional optimization, the absorbing surface 112 c or 112 d couldbe replicated and positioned to receive the peaks in the beam profiles680. The sizes of the replicated absorbing surfaces 112 c or 112 d canvary since the sizes of the peaks in the beam profiles 680 can alsovary.

Although FIGS. 6A through 6E illustrate examples of beam profiles basedon which absorbing surfaces of beam dumps could be tailored, variouschanges may be made to FIGS. 6A through 6E. For example, Gaussian, mesa,annular, Laguerre-Gaussian, and Hermite-Gaussian distributions couldvary and need not have the exact forms shown in FIGS. 6A through 6E.Also, laser beams could have other distributions not shown here, andabsorbing surfaces of beam dumps could be tailored as needed to thoseother distributions. In addition, the above description has presentedexample ways in which the absorbing surfaces 112 a-112 e could betailored for use with the beam profiles shown in FIGS. 6A through 6E.This is for illustration and explanation only. Any other suitableabsorbing surfaces could be used with the beam profiles shown in FIGS.6A through 6E or other beam profiles.

FIGS. 7A and 7B illustrate example results that could be obtained usinga beam dump having an absorbing surface tailored to a beam profile for ahigh-energy laser system or other system according to this disclosure.In particular, FIG. 7A illustrates an example temperature distribution700 in a cross-section of a beam dump that receives laser energy havinga Gaussian distribution (the beam profile 600), where an absorbingsurface of the beam dump is a simple inverted straight cone. FIG. 7Billustrates an example temperature distribution 750 in a beam dump 100that receives the same laser energy, but the beam dump 100 includes theabsorbing surface 112 a. Both beam dumps are formed using the samematerials and absorptive coatings.

As shown in FIG. 7A, because the absorbing surface of the beam dump is asimple inverted cone, the absorbing surface narrows from a larger end702 to a tip 704. Given the Gaussian distribution of the laser energy inthe beam, the bulk of the laser energy is absorbed at or near the tip704 of the inverted cone. As a result, the temperature distribution 700shows that the tip 704 of the absorbing surface experiences much highertemperatures than other portions of the absorbing surface. In somesimulations, the maximum temperature experienced by this absorbingsurface occurs at the very end of the tip 704 and could reach atemperature of about 365° C. Also, in some simulations, the totaltemperature range experienced by the entire absorbing surface here couldrange from about 110° C. to about 365° C.

As shown in FIG. 7B, because the absorbing surface 112 a of the beamdump 100 is tailored more to the beam profile 600, the temperaturedistribution 750 of the absorbing surface 112 a is spread out much morecompared to the temperature distribution 700. While there is still a“hot spot” in the temperature distribution 750, the hot spot is spreadout over a much larger area of the absorbing surface 112 a. In somesimulations, the maximum temperature experienced by the absorbingsurface 112 a could reach a temperature of about 115° C., and the totaltemperature range experienced by the entire absorbing surface 112 acould range from about 70° C. to about 115° C. This is significantlylower than the maximum temperature and temperature range in thetemperature distribution 700, and it is achieved using the samematerials and absorptive coatings. As can be seen here, while notobtaining a uniform temperature distribution, the beam dump 100 is ableto obtain a temperature distribution 750 that is much more even comparedto the temperature distribution 700. More even energy distribution couldbe obtained by using the absorbing surface 112 b or by performingtwo-dimensional distribution as described above.

Although FIGS. 7A and 7B illustrate examples of results that could beobtained using a beam dump having an absorbing surface tailored to abeam profile for a high-energy laser system or other system, variouschanges may be made to FIGS. 7A and 7B. For example, the temperaturedistributions 700 and 750 shown here are examples based on specificsimulations. Actual implementations of a beam dump having an invertedstraight cone and actual implementations of the beam dump 100 couldexperience other temperature distributions. Also, other temperaturedistributions could be obtained in the beam dump 100 using otherabsorbing surfaces, such as those described above.

FIG. 8 illustrates an example high-energy laser system 800 according tothis disclosure. As shown in FIG. 8, the system 800 includes multiplelasers 802, including a high-energy laser (HEL) and an alignment laser.The high-energy laser generally operates to produce a high-energy laserbeam 804, which is output from the system 800. The alignment lasergenerally operates to produce a much lower-energy alignment beam 806,which is used to control the alignment of the high-energy beam 804 withother components of the system 800. Each laser 802 could be implementedin any suitable manner. In some embodiments, the high-energy laser isimplemented using a master-oscillator source that generates a low-energybeam and a power amplifier (such as a planar waveguide) that amplifiesthe low-energy beam and generates the high-energy beam 804.

A beam controller 808 operates to reposition or otherwise prepare thehigh-energy beam 804 for output from the system 800. A beam splitter 810allows the bulk of the high-energy beam 804 to pass through the beamsplitter 810 to output optics 812, while the beam splitter 810 reflectsthe alignment beam 806. The output optics 812 focus the high-energy beam804 or otherwise relay the high-energy beam 804 out of the system 800.The beam controller 808 includes any suitable structure for modifying ahigh-energy beam. The beam splitter 810 includes any suitablestructure(s) for splitting optical signals. The output optics 812include any suitable optical device(s) for directing or formattingoptical signals.

Ideally, the beam splitter 810 would pass all laser energy in thehigh-energy beam 804 to the output optics 812. In reality, however, someenergy in the high-energy beam 804 reflects from the beam splitter 810and continues to travel with the alignment beam 806. This residual orleakage energy from the high-energy beam 804 needs to be terminated, orit could damage other components of the laser system 800. Here, aleakage beam splitter 814 reflects most or all of the residual HELenergy to a beam dump 816 and passes the alignment beam 806 to a laserdiagnostics unit 818. The beam dump 816 includes an absorbing surfacetailored to the profile of the incoming residual energy (which matchesor closely resembles the beam profile of the high-energy beam 804) andterminates all or substantially all of the residual energy. The beamsplitter 814 includes any suitable structure(s) for splitting opticalsignals. The beam dump 816 could represent the beam dump 100 describedabove, although the exact form of the beam dump 816 could vary as neededor desired.

The laser diagnostics unit 818 generally operates to analyze thealignment beam 806 and make changes to the beam controller 808. This mayallow, for example, the laser diagnostics unit 818 to change how thebeam controller 808 is directing the high-energy beam 804. Thediagnostics unit 818 includes any suitable structure for analyzing dataand making adjustments to a high-energy laser beam.

Although FIG. 8 illustrates one example of a high-energy laser system800, various changes may be made to FIG. 8. For example, while thesystem 800 represents one example use of a beam dump having an absorbingsurface tailored to a beam profile, such beam dumps could be used in anyother suitable system. Also, while the beam dump 816 is shown here asterminating residual energy from a high-energy beam 804, a beam dumphaving an absorbing surface tailored to a beam profile could be used toterminate any other suitable laser energy.

FIG. 9 illustrates an example method 900 for fabricating and using abeam dump having an absorbing surface tailored to a beam profile in oneor more dimensions for a high-energy laser system or other systemaccording to this disclosure. For ease of explanation, the method 900 isdescribed as involving the beam dump 100 having an absorbing surface 112a-112 e being used as the beam dump 816 in the system 800 of FIG. 8.However, the method 900 could involve any suitable beam dump having anysuitable tailored absorbing surface, and the beam dump could be used inany suitable system.

As shown in FIG. 9, an expected profile of beam energy to be terminatedby a beam dump is identified at step 902. This could include, forexample, using equipment to measure the actual intensities of a beamprofile for a laser beam or running simulations to identify the expectedintensities of a beam profile for a laser beam. In some embodiments, theexpected profile could be a Gaussian, mesa, annular, Laguerre-Gaussian,or Hermite-Gaussian distribution, although other beam profiles couldalso be identified.

A design for an absorbing surface of a beam dump is identified based onthe expected beam profile at step 904. This could include, for example,designing an absorbing surface so that one or more portions of theabsorbing surface would have one or more larger angles of incidence withrespect to the beam energy in more intense portions of the beam profile.This could also include designing the absorbing surface so that one ormore portions of the absorbing surface would have one or more smallerangles of incidence (possibly a zero angle of incidence) with respect tothe beam energy in less intense portions of the beam profile. Theportions with the different angles of incidence could be arranged alonga single dimension or in multiple dimensions.

A beam dump having the designed absorbing surface is fabricated at step906. This could include, for example, fabricating the beam dump 100 withthe desired design for the absorbing surface within a cavity defined bythe housing 104 of the beam dump 100. Various manufacturing techniquesfor fabricating the beam dump 100 (either integrally or as separateconnected components) are provided above. The beam dump is installed ina laser system at step 908. This could include, for example, attachingthe base 102 of the beam dump 100 to a larger structure.

At this point, one or more lasers can be operated in the laser system atstep 910, and laser energy is received at the absorbing surface of thebeam dump at step 912. This could include, for example, operating thelasers 802 and other components of the laser system 800 and receivingresidual laser energy at the beam dump. The received laser energy isabsorbed at the beam dump and converted into thermal energy at step 914,and the thermal energy is removed from the beam dump at step 916. Thiscould include, for example, the absorbing surface of the beam dumpabsorbing most or all of the incoming laser energy. Any laser energyreflected from the absorbing surface is ideally absorbed by othercomponents of the beam dump. This could also include using passive oractive cooling to remove the thermal energy from the absorbing surface.

Although FIG. 9 illustrates one example of a method 900 for fabricatingand using a beam dump having an absorbing surface tailored to a beamprofile in one or more dimensions for a high-energy laser system orother system, various changes may be made to FIG. 9. For example, whileshown as a series of steps, various steps in FIG. 9 could overlap, occurin parallel, occur in a different order, or occur any number of times.Also, different entities could perform different steps of FIG. 9, suchas when different entities design, fabricate, install, and use the beamdump. Thus, for instance, steps 902-908 could be performed separatelyfrom steps 910-916 (although other subdivisions of the steps could alsobe used).

It may be advantageous to set forth definitions of certain words andphrases used throughout this patent document. The terms “include” and“comprise,” as well as derivatives thereof, mean inclusion withoutlimitation. The term “or” is inclusive, meaning and/or. The phrase“associated with,” as well as derivatives thereof, may mean to include,be included within, interconnect with, contain, be contained within,connect to or with, couple to or with, be communicable with, cooperatewith, interleave, juxtapose, be proximate to, be bound to or with, have,have a property of, have a relationship to or with, or the like. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

The description in this patent document should not be read as implyingthat any particular element, step, or function is an essential orcritical element that must be included in the claim scope. Also, none ofthe claims is intended to invoke 35 U.S.C. § 112(f) with respect to anyof the appended claims or claim elements unless the exact words “meansfor” or “step for” are explicitly used in the particular claim, followedby a participle phrase identifying a function. Use of terms such as (butnot limited to) “mechanism,” “module,” “device,” “unit,” “component,”“element,” “member,” “apparatus,” “machine,” “system,” “processor,”“processing device,” or “controller” within a claim is understood andintended to refer to structures known to those skilled in the relevantart, as further modified or enhanced by the features of the claimsthemselves, and is not intended to invoke 35 U.S.C. § 112(f).

While this disclosure has described certain embodiments and generallyassociated methods, alterations and permutations of these embodimentsand methods will be apparent to those skilled in the art. Accordingly,the above description of example embodiments does not define orconstrain this disclosure. Other changes, substitutions, and alterationsare also possible without departing from the spirit and scope of thisdisclosure, as defined by the following claims.

What is claimed is:
 1. A system comprising: a laser configured togenerate laser energy having a profile, the laser energy having anon-uniform energy distribution in the profile such that at least onefirst portion of the laser energy is more intense than at least onesecond portion of the laser energy; and a beam dump comprising anabsorbing surface, the absorbing surface configured to absorb the laserenergy and convert the laser energy into thermal energy; wherein a shapeof the absorbing surface is based on the profile of the laser energysuch that: at least one first portion of the absorbing surface has oneor more first angles of incidence with respect to the laser energy andis configured to receive the at least one first portion of the laserenergy; and at least one second portion of the absorbing surface has oneor more second angles of incidence with respect to the laser energy andis configured to receive the at least one second portion of the laserenergy; and wherein the one or more first angles of incidence are largerthan the one or more second angles of incidence.
 2. The system of claim1, wherein the absorbing surface is configured such that the at leastone first portion of the laser energy expands over the at least onefirst portion of the absorbing surface to a greater extent than the atleast one second portion of the laser energy expands over the at leastone second portion of the absorbing surface.
 3. The system of claim 1,wherein the absorbing surface is configured to expand the at least onefirst portion of the laser energy in a single dimension.
 4. The systemof claim 1, wherein: the at least one first portion of the absorbingsurface comprises one or more first flat faces; the at least one secondportion of the absorbing surface comprises one or more second flatfaces; and the first and second flat faces are arranged linearly.
 5. Thesystem of claim 1, wherein: the at least one first portion of theabsorbing surface comprises one or more first curved surfaces; the atleast one second portion of the absorbing surface comprises one or moresecond curved surfaces; and the first and second curved surfaces arearranged linearly.
 6. The system of claim 1, wherein the absorbingsurface is configured to expand the at least one first portion of thelaser energy in multiple dimensions.
 7. The system of claim 1, wherein:the shape of the absorbing surface comprises an exponential cone; the atleast one first portion of the absorbing surface comprises a tip of theexponential cone; and the at least one second portion of the absorbingsurface comprises a base of the exponential cone.
 8. The system of claim1, wherein: the shape of the absorbing surface comprises a truncatedexponential cone; the at least one second portion of the absorbingsurface comprises a central portion of the truncated exponential coneand a base of the truncated exponential cone; and the at least one firstportion of the absorbing surface comprises a surface between the centralportion of the truncated exponential cone and the base of the truncatedexponential cone.
 9. The system of claim 1, wherein the non-uniformenergy distribution in the profile is one of: a Gaussian distribution, aflat-top distribution, an annular distribution, a Laguerre-Gaussiandistribution, or a Hermite-Gaussian distribution.
 10. The system ofclaim 1, wherein: the beam dump further comprises a housing that definesa cavity in which the absorbing surface is positioned; and the housingis configured to absorb additional laser energy that reflects from andis not absorbed by the absorbing surface.
 11. A method comprising:receiving laser energy having a profile, the laser energy having anon-uniform energy distribution in the profile such that at least onefirst portion of the laser energy is more intense than at least onesecond portion of the laser energy; and absorbing the laser energy usinga beam dump comprising an absorbing surface, the absorbing surfaceconverting the laser energy into thermal energy; wherein a shape of theabsorbing surface is based on the profile of the laser energy such that:at least one first portion of the absorbing surface has one or morefirst angles of incidence with respect to the laser energy and receivesthe at least one first portion of the laser energy; and at least onesecond portion of the absorbing surface has one or more second angles ofincidence with respect to the laser energy and receives the at least onesecond portion of the laser energy; and wherein the one or more firstangles of incidence are larger than the one or more second angles ofincidence.
 12. The method of claim 11, wherein the laser energy expandsover the at least one first portion of the absorbing surface to agreater extent than the at least one second portion of the laser energyexpands over the at least one second portion of the absorbing surface.13. The method of claim 11, wherein the absorbing surface expands the atleast one first portion of the laser energy in a single dimension. 14.The method of claim 11, wherein: the at least one first portion of theabsorbing surface comprises one or more first flat faces; the at leastone second portion of the absorbing surface comprises one or more secondflat faces; and the first and second flat faces are arranged linearly.15. The method of claim 11, wherein: the at least one first portion ofthe absorbing surface comprises one or more first curved surfaces; theat least one second portion of the absorbing surface comprises one ormore second curved surfaces; and the first and second curved surfacesare arranged linearly.
 16. The method of claim 11, wherein the absorbingsurface expands the at least one first portion of the laser energy inmultiple dimensions.
 17. The method of claim 11, wherein: the shape ofthe absorbing surface comprises an exponential cone; the at least onefirst portion of the absorbing surface comprises a tip of theexponential cone; and the at least one second portion of the absorbingsurface comprises a base of the exponential cone.
 18. The method ofclaim 11, wherein: the shape of the absorbing surface comprises atruncated exponential cone; the at least one second portion of theabsorbing surface comprises a central portion of the truncatedexponential cone and a base of the truncated exponential cone; and theat least one first portion of the absorbing surface comprises a surfacebetween the central portion of the truncated exponential cone and thebase of the truncated exponential cone.
 19. The method of claim 11,wherein the non-uniform energy distribution in the profile is one of: aGaussian distribution, a flat-top distribution, an annular distribution,a Laguerre-Gaussian distribution, or a Hermite-Gaussian distribution.20. The method of claim 11, wherein: the beam dump further comprises ahousing that defines a cavity in which the absorbing surface ispositioned; and the method further comprises absorbing, using thehousing, additional laser energy that reflects from and is not absorbedby the absorbing surface.